1. Field of the Invention
The subject invention relates to an impact energy-absorbing module for dissipating energy during impact of an object.
2. Description of the Prior Art
Many products are vulnerable to injurious forces resulting from an impact, e.g., vehicles, helmets, and the like. These products-must be able to absorb a significant percentage of the energy from an impact. In the past, this has been accomplished by providing the assembly with an energy-absorbing device for supporting deformation of the assembly in order to absorb the energy from the impact.
Within the vehicle, for example, occupants require protection from an impact with structural body components such as door pillars, frames and headrails. These components are typically made of steel tubing or steel channels which are welded together to form the structural cage or unitized body for the vehicle, and may themselves become deformed as a result of the impact. Energy absorbers have been placed over the door pillars, frames, headrails and other parts of the vehicle behind interior trim to protect the vehicle occupants. Prior art approaches have used energy absorbing urethanes, polystyrene, rigid polymeric foams, blocks or cells or vanes of engineered plastics, and various sheet metal configurations, metal beams, honeycombed metal, and other geometric solids for absorbing energy. These devices, however, generally absorb less than the desired amount of energy for a given displacement, and have often produced inconsistent results.
U.S. Pat. No. 5,549,327 discloses an energy impact absorber having a stepped wall encircling a central axis. Each of the stepped walls yields an equivalent sheering force as does the next stepped wall, regardless of the thickness of the wall. A significant amount of the energy absorption is lost when a wall sheers. If the stepped wall does not sheer, energy will continue to be transferred throughout the energy absorber to walls that have not yet been deformed.
Therefore, a need exists for an energy absorbing device which maximizes energy absorption, and provides repeatable energy absorbing results. Additionally, the energy-absorbing device should have the ability to consistently dissipate a wide range of energy thresholds.
The subject invention provides an energy absorption module including at least one cell having a first wall extending upwardly along and encircling an axis, a second wall extending about the axis within and closer to the axis than the first wall. The cell is characterized by including a first step wall horizontally interconnecting the first and second walls and having a greater thickness than the second wall for assuring collapse of the second wall before the collapse of the first wall in response to a force applied to the second wall.
The invention also includes a method of molding the module by injection of an organic polymeric material into a cavity formed in mold parts to define the novel configuration of the cell.
Because the first step wall includes a thickness greater than that of the first and second walls the deformation of the cell when subjected to an impact force can be controlled. The increased thickness of the step wall prevents the first wall from shearing from the second wall during the impact. Thus, amount of energy absorption provided by each cell can be increased, and predetermined by the thickness of the step wall.
The energy-absorbing device of the subject invention optimizes the amount of energy absorption by utilizing the cells having the connecting steps of varying thicknesses. Additionally, each cell allows the subject invention to absorb a wide range of energy thresholds and produce repeatable energy dissipation results. The amount of energy absorbed by each cell can be precisely determined due to the introduction of various numbers and dimensions of the cells because the exact location and amount of the energy absorption may be determined.